1. Field of the Invention
The present invention relates to a keyless security system and, more particularly, to a keyless security system equipped with a portable transmitter and a vehicle-mounted receiver which receives a remote control signal supplied from the portable transmitter so as to lock or unlock a vehicular door lock mechanism and which also monitors each section of the vehicle when not in use and issues an alarm if any anomalies are detected.
2. Description of the Related Art
A conventional keyless security system is constructed by a portable transmitter and a vehicle-mounted receiver. When the vehicle is not in use, the vehicle-mounted receiver monitors for the motion of the vehicle, a shock applied to the vehicle, an opened door, a broken window, and other anomalies. The vehicle-mounted receiver serves as a vehicular security system for sounding an alarm if it detects such an anomaly and it also serves as a vehicular key to lock and unlock a vehicular door in response to the remote control signal received from the portable transmitter.
FIGS. 7A and 7B are schematic diagrams showing an outline of the construction of the aforesaid known keyless security system; FIG. 7A shows the construction of the portable transmitter and FIG. 7B shows the construction of the vehicle-mounted receiver.
The system illustrated in FIGS. 7A and 7B includes a portable transmitter 50, a button control panel 51, an unlock button (disarm button) 51-1, a lock button (arm button) 51-2, a remote control processing unit 52, a transmitting unit 53, a transmitting antenna 54, a vehicle-mounted receiver 60, a receiving antenna 61, a receiving module 62, a control unit 63, a power switch 64, a line voltage regulator 65, a door lock device 71, a door sensor 72, a motion sensor 73, a shock sensor 74, a glass sensor 75, a siren driver circuit 76, and a headlight blinker circuit 77.
The portable transmitter 50 includes the button control panel 51 which has the lock button 51-1 and the unlock button 51-2 for setting the lock/unlock condition of the vehicular door lock mechanism, the remote control processing unit 52 for issuing data signals corresponding to the aforesaid buttons 51-1 and 51-2, respectively, the transmitting unit 53 for converting the aforesaid data signals into remote control signals, and the transmitting antenna 54 for transmitting the remote control signals. The vehicle-mounted receiver 60 includes the receiving antenna 61 for receiving the remote control signals, a receiving module 62 which receives the remote control signals and supplies an electric field intensity detection signal SQ based on the remote control signals and the aforesaid data signal to the control unit 63, the control unit 63 which monitors each section of the vehicle and issues an alarm if any anomaly is detected, and also controls the locking and unlocking of the vehicular lock mechanism in response to the aforesaid data signal, the power switch 64 which turns ON/OFF the power to the receiving module 62, and the voltage regulator 65 which regulates the line voltage.
In connection with the construction stated above, the function for the vehicular security will be first described first. When the vehicle is not in use, if the vehicle-mounted receiver 60 is set in a security mode, then the control unit 63 is alternately switched in a fixed cycle between a control-activated condition, under which each section is monitored at high speed, and a standby condition, under which no monitoring control is carried out in the subsystem clock mode, so as to minimize the power consumed by the vehicle-mounted receiver 60. During the control-activated condition, the control unit 63 monitors for an opened door through the door sensor 72, vehicle motion through the motion sensor 73, a shock applied to the vehicle through the shock sensor 74, and a broken window through the glass sensor 75. If any of the anomalies is detected, the control unit 63 actuates the siren driver circuit 76 to give an audible alarm such as siren and/or actuates the headlight blinker circuit 77 to flash the headlight. The control unit 63 issues such an audible alarm to signal the anomaly of the vehicle; it issues no alarm if none of the aforesaid anomalies are detected.
The operation for locking and unlocking the vehicular door will now be described. Under the control-activated condition, the control unit 63 monitors for anomalies and also supplies control signal V.sub.TCONT to the power switch 64. While control signal V.sub.TCONT is being supplied, the power switch 64 functions to supply the line voltage obtained through the line voltage regulator 65 to the receiving module 62 so as to set the receiving module 62 ready for receiving the remote control signal. While the receiving module 62 is ready for receiving the remote control signal, if the lock button 51-1 or the unlock button 52-2 of the button control panel 51 of the portable transmitter 50 is operated, then the data signal, which corresponds to the button operation, is generated in the remote control processing unit 52. The data signal thus generated is converted into the remote control signal through the transmitting unit 53 before it is transmitted through the transmitting antenna 54. When the receiving module 62 of the vehicle-mounted receiver 60 receives the transmitted remote control signal through the receiving antenna 61, the receiving module 62, which is ready for receiving the remote control signal, processes the received remote control signal and supplies electric field detection signal SQ (representing electric field of the remote control signal and demodulated data signal DATA) to the control unit 63. Upon receipt of electric field detection signal SQ, the control unit 63 switches the periodic control-activated condition over to the continuous control-activated condition. At the same time, the control unit supplies continuous control signal V.sub.TCONT to the power switch 64 and it also sets the receiving module 62 for receiving continuous remote control signals. Thus, the receiving module 62 becomes ready to receive the remote control signals which are supplied in succession. The control unit 63 drives the door lock device 71 in accordance with the contents of data signal DATA supplied from the receiving module 62, thereby locking or unlocking the vehicular door key.
FIG. 8 is the block diagram showing the details of the configuration of the receiving module 62 in the known keyless security system illustrated in FIG. 7B.
The receiving module 62 shown in FIG. 8 includes a signal receiver 80, a high-frequency band-pass filter 81, a high-frequency amplifier 82, a frequency mixer circuit 83, a local oscillator 84, an intermediate-frequency (IF) band-pass filter 85, an IF amplifier 86, a demodulating unit 87, a signal processor 90, a low-pass filter 91, a comparator circuit 92, an electric field detector 95, a band-pass filter 96, an electric field intensity detector 97, and a comparator circuit 98. Other composing elements which are identical to those shown in FIG. 7B are assigned the same reference numerals.
The signal receiver 80 includes the high-frequency band-pass filter 81 for removing the frequency components to isolate the effective frequency component from a received remote control signal, the high-frequency amplifier 82 for amplifying the filtered remote control signal as necessary, the local oscillator 83 for generating a local oscillation frequency signal, the frequency mixer circuit 84 for mixing the remote control signal with the local oscillation frequency signal and for generating an IF signal, the IF band-pass filter 85 for removing unnecessary frequency components from the IF signal, the filtered IF amplifier 86 for amplifying the IF signal as necessary, and the demodulating unit 87 for demodulating the filtered IF signal to obtain a data signal. The signal processor 90 includes the low-pass filter for removing unnecessary frequency components to leave the data signal component, and the comparator circuit 92 for comparing the data signal with a predetermined level so as to obtain the required data signal DATA. The electric field detector 95 is comprised of the band-pass filter 96 for removing the required frequency component which contains the data signal component, the electric field intensity detector 97 for detecting the electric field intensity of the filtered data signal, and the comparator circuit 98 for comparing the detected electric field intensity with a predetermined level to obtain required field electric detection signal SQ.
In this case, the procedure for processing the remote control signal received by the signal receiver 80 (i.e., the steps of the procedure for generating the demodulation data signal from the received remote control signal) is the same as the procedure for the demodulation carried out by the AM receiver or the like (if the remote control signal is of an AM-modulated wave). Such a demodulating procedure is well known in the technical field; therefore, a description of the procedure for processing the remote control signal received by the signal receiver 80 will be omitted.
In the signal processor 90, the data signal generated by the signal receiver 80 first passes through the low-pass filter 91 so that the unwanted frequency components are removed to isolate the data signal component, then the filtered data through the comparator circuit 92 which compares the data signal component with the predetermined level to remove noise components before the data signal component is output as the required data signal DATA. In the electric field detector 95, the data signal produced by the signal receiver 80 first goes through the band-pass filter 96 to remove the required frequency component which contains the data signal component, then the resulting signal passes through the electric field detector 97 to detect the electric field intensity of the data signal. The detected electric field intensity is then with the predetermined level by the comparator circuit 98 before the data signal is output as the required electric field detection signal SQ.
The known keyless security system described above is designed to generate the electric field detection signal SQ by the electric field detector 95 of the vehicle-mounted receiver 60 and to supply the electric field detection signal SQ to the control unit 63, thereby placing the control unit 63 in the continuous control-activated mode and also setting the receiving module 62 for receiving continuous remote control signals. This requires that the vehicle-mounted receiver 60 be provided with the electric field detector 95, which serves solely as the detector of the electric field intensity of the remote control signal, resulting in a complicated structure and higher cost of the vehicle-mounted receiver 60.